The present invention relates to mining machines of the general type shown, for example, in U.S Pat. No. 4,023,861. Such mining machines are provided with means for traversing a ground surface, usually caterpillars on either side of the machine frame, and have a universally-pivotal carrier arm of variable length which carries at its end a cutter drum rotatable about an axis parallel to the carrier arm axis or about the carrier arm axis itself.
In certain mining machines of this type, such as that shown in German patent application No. P 34 00 246.4, the shearing drum narrows toward the forward end of the drum and has a convex periphery and a rounded drum apex. A mining machine of this type is required to cut tunnels or mine roadways with a very smooth wall. The smoothness requirement cannot be met with a cylindrical cutter drum nor by one which narrows frustum-fashion, even when the peripheral surface of the drum is convex as in the case of the aforementioned German patent application. The irregularities which arise in the mine roadway walls are due to the fact that the pivotal axis of the cutter drum carrier arm is at the center of the roadway, meaning that the cutter drum intersects the walls at an angle; and the forward end of the drum penetrates further into the wall than its trailing end. The result is steps or ribs in the walls which must be removed to achieve the required wall smoothness. As a rule, after a cut of mine material is removed equal to approximately the length of the cutter drum, the roadway wall is smoothed by the drum making a finishing or profiling cut. At this end, the cutter drum moves backwardly from the mine face in order to contact and remove a step or rib as much as possible over its entire width.
In the use of a mining machine of the type described above, the vision of the machine operator is materially restricted by the dust evolved when the drum clears the face being mined. As a result, it is difficult for the machine operator to move the drum into the face by an amount corresponding to the drum length in order to limit the extent of the step or rib; and it is even more difficult for the operator to return the machine in the subsequent profiling or finishing cut to an intended position in which the drum can engage the remaining rib exactly in its highest part, reduce it substantially, and provide optimal smoothing of the exposed road wall.